In our project, we will be determining how much light bends as it passes through different substances and through substances at different temperatures.
This process is known as refraction. The amount that it refracts is known as index of refraction. The person who discovered refraction and index of refraction was Willebrord van Roijen Snell who discovered it in 1621, but his theory wasn’t published until 1703. In it he came up with a formula to describe the relationship: n1sinθ1=n2sinθ2. In words this means that the refraction index of one substance times the angle of refraction equals the refraction index of another substance times its angle of refraction. In order to find what is needed for this experiment, the second angle must be solved for algebraically by dividing the other side by n2 then taking the sine inverse (sin-1) of the other side: θ2 = sin-1(n1sinθ1 / n2). [1][2]
To do this experiment, a laser must be shone through various substances. The first person to actually create a laser was Arthur L. Schawlow. Born in 1921, he had difficulties getting a college education during the Great Depression of the 1930s, however he did receive a scholarship, and worked part time to pay for it. He helped with the war effort in 1941 by teaching to army personnel. He later got a doctorate and eventually worked with Charles Townes, who helped him to build the first laser. At the time he was actually working on a similar device known as a maser (Microwave Amplification by Stimulated Emission of Radiation) until 1957 when he decided to shorten the wavelength of it to create the laser. He later went on to win the Nobel Prize in physics in 1981. [3][4]
Lasers (Light Amplification by Stimulated Emission of Radiation) are concentrated beams of light that are monochromatic (one color). They are different from regular light in that they are only one color and they go in a single direction, which makes them perfect for the experiment. Lasers, basically defined, are machines that use atoms that shoot out photons all at once through a crystal that gives it its character color. [5][6]
In order to understand what the earlier equation, one must first understand what density is. Density was first studied and discovered over 2000 years ago by Archimedes. Archimedes was a famous astronomer, physicist, mathematician, and all-around genius. He was born in 287 B.C. died 212 B.C. and lived his life mostly in Syracuse, Sicily (Italy). He worked Pi out farther than anyone else had, invented new war machines and most importantly, figured out how to measure the volume and density of irregularly shaped objects. As the story goes, one day Archimedes was taking a bath, when he noticed that the more of him that was in the tub, the higher the water level rose, so he then running through the streets naked shouting, “Eureka” meaning I found it. He applied this discovery by dropping the king’s crown in water and also dropping silver in water and gold in water to discover that the crown was not all gold. Using this, he was able to discover the formula for density. [7][8]
Simply defined, density is the amount of matter in a certain amount of area. The formula for this is D = m/v or density equals mass divided by volume. Density varies from substance to substance, but within that substance, the density can be changed by adding or taking away energy. If enough energy is added or taken away from a substance, it could change phases. The less energy it has, the more likely it is to be a solid, add a little more, it could change to a liquid, add a lot, it could change into a gas. [9][10]
Energy added and taken away can be explained by thermodynamics. The first serious work on thermodynamics began in 1824 by French physicist Nicolas Léonard Sadi Carnot. Carnot, born in 1796 in Paris, was an intelligent child who grew up with an education from his father. He was accepted at sixteen to the École Polytechnique a prestigious french college. During this time, he joined Napoleon in a failed attempt to defend Vincennes. After a brief career in the army, he began to study gases, in particular, steam engines. In his study, he eventually discovered the laws of thermodynamics, and in 1824 wrote a book on it called Réflexions sur la puissance motrice du feu et sur les machines propres à développer cette puissance which means Reflections on the Motive Power of the Fire. This was all largely ignored at the time, and wasn’t widely accepted until ten years later when a publication of a similar document was out. He later died in 1832, two years before he became famous. [11][12]
There are three laws of thermodynamics. The first states that energy cannot be created or destroyed. What is input is what is output. The second states that heat or energy is transferred from highest energy to lowest energy, never the other way around. The third law states that temperature can never reach absolute zero. This refers to the measurement of temperature in a unit called Kelvin. Using Kelvin, zero refers to an object possessing no energy or heat whatsoever. It is approachable, but impossible to reach. A fourth law also exists, but it is referred to as the zeroth law. It states that if two objects have the same temperature as another, then they must have the same temperature as each other. This may seem obvious, but it is very important.[13][14]
Lab Notebook
Purpose
To determine the index of refraction of various substances based on their density and temperature.
Introduction:
In this experiment, we hope to prove that density and temperature affect how much light refracts. If the substance has more density then light will refract more. If the substance is at a higher temperature then light will refract less.
When heating the substances, be sure to wear goggles and gloves. Use clamps when transferring heated substances from one location to another. Do not look directly into the laser. Turn off the laser when it is not being used. Do not drink the substances. Wash hands before and after experiment.
Planned Procedure:
1. First we need to collect our materials: a laser pointer, identical graduated cylinders, clamp to hold laser, clamps to hold the cylinders, a protractor, a white sheet of poster-board, a pen or pencil, measuring tape, a refrigerator, some heating device, a thermometer, a triple-beam balance scale, milk, water, apple juice, rubbing alcohol, and cooking oil. The latter five are the substances being measured. 2. Next we need to measure the cylinder’s mass on the scale and also their individual index of refraction at cold, room-temperature, and heated conditions (approximately 3 C, 22 C, 50 C). (Air also refracts light but it is minimal enough to neglect). 1. To measure the index of refraction, start by putting the white poster-board against a wall and make sure it is flat. 2. Set up a clamp so that the laser set up on it is at a 90 degree angle to the table it is set upon. Check with a protractor. 3. Set up a spot in-between the poster-board and laser on the table so that all three form a straight line and mark the spot. 4. Shine the laser against the poster-board and mark that spot as the reference point. 5. Measure the diameter of a cylinder. 6. Set the cylinder so that the center of it is in the spot previously marked on the table. 7. Shine the laser through the cylinder and mark its new spot on the poster-board. 3. Now separate the substances into their respective cylinders, making sure to pour them as evenly as possible, three per substance, and measure their masses. 4. Put one of each substance into the refrigerator, out in the open, and put the last to the side. 5. Take measure of the room temperature’s cylinders’ volume and temperature. 6. Repeat steps 2.6-2.7 with each substance for room temperature, making sure to mark what the substance is, and its temperature on the poster-board. Leave the substances set aside alone for now. 7. Now take the substances that are set aside and heat one of them to 50 degrees Celsius. 8. Quickly but accurately measure the current volume of the heated substance. 9. Use clamps to move the cylinder, carefully, to the marked spot, repeating step 6. 10. Repeat last three steps for the remaining substances set aside. 11. By now the refrigerated substances should be cooled, so take them out, one at a time, and repeat steps 5-6 for refrigerated substances. 12. Make calculations and be sure to use the diameters in step 2.5 to find the index of refraction.
1. First we gathered the supplies: a red laserjuice, thirteen 25 mL graduated cylinders, a clamp to hold the laser, a white poster-board, a pen, a pencil, a ruler, a refrigerator, and icebox holding milk and cranberry juice, a Bunsen burner, a thermometer, a triple beam balance scale, cooking oil, water, a pipette with a bulb, and a ceramic tile. 2. Using a pipette, I filled each cylinder about halfway(except for one). 3 with milk, 3 with water, 3 with cooking oil, and 3 with cranberry juice. 3.Then we took the left over cylinder and measured its mass. Then we measured all of the other cylinder’s masses. 4. Running out of time, we put all of the milk and cranberry juice cylinders along with one water and one cooking oil cylinder inside the refrigerator so that they wouldn’t spoil overnight. We labeled them all 1-12 so we could keep track of what they represented data wise. 5. The next morning we took out two of the milk and cranberry juice cylinders. We separated all of the substances so that one of each was in the refrigerator, one of each was next to the equipment, and one of each was next to the Bunsen burner on the adjacent table, according to what we labeled them. 6. Next we shined the laser on the poster board so that it was at a 90 degree angle to the table and tightened the clamp. We marked its location, on the poster board that we taped up to the wall across from it, in pen. We labeled the spot as the origin. 7. Then we took the unused graduated cylinder and positioned it on top of the ceramic tile and positioned that to where the laser would shine directly through the center of it. We then duct taped the clamp holding the laser and the ceramic disc to the table so that they wouldn’t move. We marked the exact positioning of the graduated cylinder on the ceramic disc with a pencil and also the laser’s position as it was shined through the cylinder on the poster-board. 8. First we took the substances from the refrigerator, one at a time, and measured their temperatures and volumes. Before taking out the next substance, we also set it on the ceramic tile so that its position exactly corresponded to what was marked earlier. Then we shone the laser through it and we marked where the beam seemed most intense and we appropriately labeled the substance and its temperature. 9. Next we took the Bunsen burner and hooked it up to the gas. We set it directly under where the clamp to hold the cylinders is. For the substances to be heated, we had to transfer them into a test tube one at a time because the chemistry teacher didn’t want us to heat the graduated cylinders. 10. We situated the test tube over the burner and tilted it away and heated the water to 50 degrees Celsius. Then we transferred it back into the graduated cylinder and lined it up with the previously marked spot on the ceramic tile. We took its volume and shined the laser through it and marked its spot. 11. We repeated the last step for milk then oil, but for cranberry juice we used another separate test tube. 12. Lastly we took the the room temperature cylinders and measured their temperature and volume. 13. We then took them one at a time, lined them up with the tile, shined the laser through them, and marked their spots. 14. Since all of the cylinders were the same, we measured the diameter of just one of the cylinders. 15. We disposed of all the substances, cleaned everything out and put it all away.
For tap water, our experiment showed that its index of refraction was lowest at 21 C and it was highest when the water was heated to 50 C. For the cooking oil, it had a higher index of refraction when it was cooled to 6 C and had the lowest index when at room temperature of 21 C. In our experiment not one of the three containers of milk allowed the laser to pass through it. While testing the cranberry juice, the lowest index of refraction was at 5 C and its highest index was at 50 C. When density was taken into account, it appeared that overall, the more dense a substance was the higher its index of refraction came out to be.
Discussion:
These results only half-way confirm our hypothesis. While the index of refraction increases with increasing density, it also increases with increasing temperature. This does not make sense. Since temperature and volume are directly related and density and volume are inversely related that means that temperature and density and inversely related so their results should be inversed as well. This is most likely due to human error and/or procedural error. The human error would have most likely happened during the shining of the laser. Because the graduated cylinders are curved, they have to be placed in the exact same position each and every time, which is nearly impossible for a human. It would have been better and easier if it were shaped as a square prism. Some procedural errors include the switch during the heating process. It caused some of the liquid to be left behind in the test tube which would have reduced the amount of liquid skewing the results. If done again, I would have just directly heated the graduated cylinder. Also a procedural error was not using a different transfer tube for each substance. Some of the milk was left over and mixed with the oil, increasing its opacity so that it did not show. To avoid this, a clean, new, test tube should have been used. Another procedural error was on the chart. Shining the laser through the cylinder created a line going form left to right but the refraction also went left to right making it difficult to mark their positions. To avoid this unforeseen error, we should have moved the chart down for each test tube and marked an origin spot for each new position. This would have also made the chart easier to label.
This video can help explain where our experiment went wrong.
Table of Contents
Laser Refraction
Background Information:
In our project, we will be determining how much light bends as it passes through different substances and through substances at different temperatures.This process is known as refraction. The amount that it refracts is known as index of refraction. The person who discovered refraction and index of refraction was Willebrord van Roijen Snell who discovered it in 1621, but his theory wasn’t published until 1703. In it he came up with a formula to describe the relationship: n1sinθ1=n2sinθ2. In words this means that the refraction index of one substance times the angle of refraction equals the refraction index of another substance times its angle of refraction. In order to find what is needed for this experiment, the second angle must be solved for algebraically by dividing the other side by n2 then taking the sine inverse (sin-1) of the other side: θ2 = sin-1(n1sinθ1 / n2). [1] [2]
To do this experiment, a laser must be shone through various substances. The first person to actually create a laser was Arthur L. Schawlow. Born in 1921, he had difficulties getting a college education during the Great Depression of the 1930s, however he did receive a scholarship, and worked part time to pay for it. He helped with the war effort in 1941 by teaching to army personnel. He later got a doctorate and eventually worked with Charles Townes, who helped him to build the first laser. At the time he was actually working on a similar device known as a maser (Microwave Amplification by Stimulated Emission of Radiation) until 1957 when he decided to shorten the wavelength of it to create the laser. He later went on to win the Nobel Prize in physics in 1981. [3] [4]
Lasers (Light Amplification by Stimulated Emission of Radiation) are concentrated beams of light that are monochromatic (one color). They are different from regular light in that they are only one color and they go in a single direction, which makes them perfect for the experiment. Lasers, basically defined, are machines that use atoms that shoot out photons all at once through a crystal that gives it its character color. [5] [6]
In order to understand what the earlier equation, one must first understand what density is. Density was first studied and discovered over 2000 years ago by Archimedes. Archimedes was a famous astronomer, physicist, mathematician, and all-around genius. He was born in 287 B.C. died 212 B.C. and lived his life mostly in Syracuse, Sicily (Italy). He worked Pi out farther than anyone else had, invented new war machines and most importantly, figured out how to measure the volume and density of irregularly shaped objects. As the story goes, one day Archimedes was taking a bath, when he noticed that the more of him that was in the tub, the higher the water level rose, so he then running through the streets naked shouting, “Eureka” meaning I found it. He applied this discovery by dropping the king’s crown in water and also dropping silver in water and gold in water to discover that the crown was not all gold. Using this, he was able to discover the formula for density. [7] [8]
Simply defined, density is the amount of matter in a certain amount of area. The formula for this is D = m/v or density equals mass divided by volume. Density varies from substance to substance, but within that substance, the density can be changed by adding or taking away energy. If enough energy is added or taken away from a substance, it could change phases. The less energy it has, the more likely it is to be a solid, add a little more, it could change to a liquid, add a lot, it could change into a gas. [9] [10]
Energy added and taken away can be explained by thermodynamics. The first serious work on thermodynamics began in 1824 by French physicist Nicolas Léonard Sadi Carnot. Carnot, born in 1796 in Paris, was an intelligent child who grew up with an education from his father. He was accepted at sixteen to the École Polytechnique a prestigious french college. During this time, he joined Napoleon in a failed attempt to defend Vincennes. After a brief career in the army, he began to study gases, in particular, steam engines. In his study, he eventually discovered the laws of thermodynamics, and in 1824 wrote a book on it called Réflexions sur la puissance motrice du feu et sur les machines propres à développer cette puissance which means Reflections on the Motive Power of the Fire. This was all largely ignored at the time, and wasn’t widely accepted until ten years later when a publication of a similar document was out. He later died in 1832, two years before he became famous. [11] [12]
There are three laws of thermodynamics. The first states that energy cannot be created or destroyed. What is input is what is output. The second states that heat or energy is transferred from highest energy to lowest energy, never the other way around. The third law states that temperature can never reach absolute zero. This refers to the measurement of temperature in a unit called Kelvin. Using Kelvin, zero refers to an object possessing no energy or heat whatsoever. It is approachable, but impossible to reach. A fourth law also exists, but it is referred to as the zeroth law. It states that if two objects have the same temperature as another, then they must have the same temperature as each other. This may seem obvious, but it is very important.[13] [14]
Lab Notebook
Purpose
To determine the index of refraction of various substances based on their density and temperature.Introduction:
In this experiment, we hope to prove that density and temperature affect how much light refracts. If the substance has more density then light will refract more. If the substance is at a higher temperature then light will refract less.Formulas:
n1sinθ1 = n2sinθ2,d = m/v,
sinθ = opp/hyp,
cosθ = adj/hyp,
tanθ = opp/adj
a2+b2=c2
Safety Information:
When heating the substances, be sure to wear goggles and gloves. Use clamps when transferring heated substances from one location to another. Do not look directly into the laser. Turn off the laser when it is not being used. Do not drink the substances. Wash hands before and after experiment.Planned Procedure:
1. First we need to collect our materials: a laser pointer, identical graduated cylinders, clamp to hold laser, clamps to hold the cylinders, a protractor, a white sheet of poster-board, a pen or pencil, measuring tape, a refrigerator, some heating device, a thermometer, a triple-beam balance scale, milk, water, apple juice, rubbing alcohol, and cooking oil. The latter five are the substances being measured.2. Next we need to measure the cylinder’s mass on the scale and also their individual index of refraction at cold, room-temperature, and heated conditions (approximately 3 C, 22 C, 50 C). (Air also refracts light but it is minimal enough to neglect).
1. To measure the index of refraction, start by putting the white poster-board against a wall and make sure it is flat.
2. Set up a clamp so that the laser set up on it is at a 90 degree angle to the table it is set upon. Check with a protractor.
3. Set up a spot in-between the poster-board and laser on the table so that all three form a straight line and mark the spot.
4. Shine the laser against the poster-board and mark that spot as the reference point.
5. Measure the diameter of a cylinder.
6. Set the cylinder so that the center of it is in the spot previously marked on the table.
7. Shine the laser through the cylinder and mark its new spot on the poster-board.
3. Now separate the substances into their respective cylinders, making sure to pour them as evenly as possible, three per substance, and measure their masses.
4. Put one of each substance into the refrigerator, out in the open, and put the last to the side.
5. Take measure of the room temperature’s cylinders’ volume and temperature.
6. Repeat steps 2.6-2.7 with each substance for room temperature, making sure to mark what the substance is, and its temperature on the poster-board. Leave the substances set aside alone for now.
7. Now take the substances that are set aside and heat one of them to 50 degrees Celsius.
8. Quickly but accurately measure the current volume of the heated substance.
9. Use clamps to move the cylinder, carefully, to the marked spot, repeating step 6.
10. Repeat last three steps for the remaining substances set aside.
11. By now the refrigerated substances should be cooled, so take them out, one at a time, and repeat steps 5-6 for refrigerated substances.
12. Make calculations and be sure to use the diameters in step 2.5 to find the index of refraction.
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Actual Procedure:
1. First we gathered the supplies: a red laser juice, thirteen 25 mL graduated cylinders, a clamp to hold the laser, a white poster-board, a pen, a pencil, a ruler, a refrigerator, and icebox holding milk and cranberry juice, a Bunsen burner, a thermometer, a triple beam balance scale, cooking oil, water, a pipette with a bulb, and a ceramic tile.2. Using a pipette, I filled each cylinder about halfway(except for one). 3 with milk, 3 with water, 3 with cooking oil, and 3 with cranberry juice.
3.Then we took the left over cylinder and measured its mass. Then we measured all of the other cylinder’s masses.
4. Running out of time, we put all of the milk and cranberry juice cylinders along with one water and one cooking oil cylinder inside the refrigerator so that they wouldn’t spoil overnight. We labeled them all 1-12 so we could keep track of what they represented data wise.
5. The next morning we took out two of the milk and cranberry juice cylinders. We separated all of the substances so that one of each was in the refrigerator, one of each was next to the equipment, and one of each was next to the Bunsen burner on the adjacent table, according to what we labeled them.
6. Next we shined the laser on the poster board so that it was at a 90 degree angle to the table and tightened the clamp. We marked its location, on the poster board that we taped up to the wall across from it, in pen. We labeled the spot as the origin.
7. Then we took the unused graduated cylinder and positioned it on top of the ceramic tile and positioned that to where the laser would shine directly through the center of it. We then duct taped the clamp holding the laser and the ceramic disc to the table so that they wouldn’t move. We marked the exact positioning of the graduated cylinder on the ceramic disc with a pencil and also the laser’s position as it was shined through the cylinder on the poster-board.
8. First we took the substances from the refrigerator, one at a time, and measured their temperatures and volumes. Before taking out the next substance, we also set it on the ceramic tile so that its position exactly corresponded to what was marked earlier. Then we shone the laser through it and we marked where the beam seemed most intense and we appropriately labeled the substance and its temperature.
9. Next we took the Bunsen burner and hooked it up to the gas. We set it directly under where the clamp to hold the cylinders is. For the substances to be heated, we had to transfer them into a test tube one at a time because the chemistry teacher didn’t want us to heat the graduated cylinders.
10. We situated the test tube over the burner and tilted it away and heated the water to 50 degrees Celsius. Then we transferred it back into the graduated cylinder and lined it up with the previously marked spot on the ceramic tile. We took its volume and shined the laser through it and marked its spot.
11. We repeated the last step for milk then oil, but for cranberry juice we used another separate test tube.
12. Lastly we took the the room temperature cylinders and measured their temperature and volume.
13. We then took them one at a time, lined them up with the tile, shined the laser through them, and marked their spots.
14. Since all of the cylinders were the same, we measured the diameter of just one of the cylinders.
15. We disposed of all the substances, cleaned everything out and put it all away.
Data:
|| Cylinder || 1 || 2 || 3 || 4 || 5 || 6 ||
|| Substance
|| Cylinder || 7 || 8 || 9 || 10 || 11 || 12 ||
|| Substance
Charts:
|| Cylinder || 1 || 2 || 3 || 4 || 5 || 6 |||| Substance
|| Cylinder || 7 || 8 || 9 || 10 || 11 || 12 ||
|| Substance
Calculations:
Substance Refraction Distance: 11.7cm - 1.6 cm = 10.1cmHypotenuse: a2+b2=c2
c = (a2 + b2)1/2
c = (1.5cm2 + 10.1cm2)1/2
c = 10.211 cm.
sinθ : sinθ = opp/adj
sinθ = 10.1/10.211
sinθ = 0.989
n2: n1sinθ1 = n2sinθ2
n2 = (n1sinθ1 / sinθ2)
n2 = 1.0002771sin(90)/0.989
n2 = 1.0114
Density: d = m/v
d = (62.379g - 44.956g)/17.6 mL
d = 0.9903g/mL
Graphs:
Results:
For tap water, our experiment showed that its index of refraction was lowest at 21 C and it was highest when the water was heated to 50 C. For the cooking oil, it had a higher index of refraction when it was cooled to 6 C and had the lowest index when at room temperature of 21 C. In our experiment not one of the three containers of milk allowed the laser to pass through it. While testing the cranberry juice, the lowest index of refraction was at 5 C and its highest index was at 50 C.When density was taken into account, it appeared that overall, the more dense a substance was the higher its index of refraction came out to be.
Discussion:
These results only half-way confirm our hypothesis. While the index of refraction increases with increasing density, it also increases with increasing temperature. This does not make sense. Since temperature and volume are directly related and density and volume are inversely related that means that temperature and density and inversely related so their results should be inversed as well. This is most likely due to human error and/or procedural error.The human error would have most likely happened during the shining of the laser. Because the graduated cylinders are curved, they have to be placed in the exact same position each and every time, which is nearly impossible for a human. It would have been better and easier if it were shaped as a square prism.
Some procedural errors include the switch during the heating process. It caused some of the liquid to be left behind in the test tube which would have reduced the amount of liquid skewing the results. If done again, I would have just directly heated the graduated cylinder. Also a procedural error was not using a different transfer tube for each substance. Some of the milk was left over and mixed with the oil, increasing its opacity so that it did not show. To avoid this, a clean, new, test tube should have been used. Another procedural error was on the chart. Shining the laser through the cylinder created a line going form left to right but the refraction also went left to right making it difficult to mark their positions. To avoid this unforeseen error, we should have moved the chart down for each test tube and marked an origin spot for each new position. This would have also made the chart easier to label.
This video can help explain where our experiment went wrong.
Sources: